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Ralph856
08-07-2012, 04:03 PM
Hi

I have a pair of LE-10H's that were refoamed by a local speaker repairer, but within several months had started audibly distorting when playing deep bass music, such as dub.

I took them back to that same company and they told me that the black foam, near the centre dome polepiece hole, had disintegrated and had fallen into the gap.

They said it took 2 hours of labour (100 or $155) to repair both drivers but that they are now 'as good as new'.

Not being a technical person, I'm just interested to know if all this sounds credible and genuine? :confused:

Incidentally, I did raise the question as to why they hadn't noticed the issue when they had done the refoam several months earlier but didn't get a clear answer back on that. I guess it's conceivable that the deterioration took place during those seven months :hmm:.

Thanks :cheers:

(BTW- this is not to be confused with a different set of LE-10's that I made a thread about recently)

Audiobeer
08-07-2012, 04:59 PM
Yes it is credible and it happens. I remove those pesky disenegrating POS on all my vintage JBLs. I sold a pair or freshly refoamed 4313B's only to have it come bach within days due to the inability of one of the woofers to move. 40Hz and it buzzed. After a little research and removal of the dust cap the exact thing you described had happened.

rdgrimes
08-07-2012, 07:49 PM
Getting to the point where that piece of foam should be removed on every woofer re-foam job, but almost nobody does it. It might be the most common cause of failure in old drivers.

Ralph856
08-08-2012, 04:19 AM
Many thanks! That's good to hear, although the combined cost of the original refoam plus latest repair would have bought a damn recone! Shame they didn't have the foresight to remove it previously.



I do have another question about refoams because I need to get my other pair of 'NIB' LE-10's done:

I called a different company to the one mentioned above and they told me that when they do a refoam of an old driver, they replace the back suspension at the same time (with a non-JBL part incidentally). Aren't refoams usually just the surround (plus that piece of foam, if you're lucky)?

rdgrimes
08-08-2012, 10:08 AM
I called a different company to the one mentioned above and they told me that when they do a refoam of an old driver, they replace the back suspension at the same time (with a non-JBL part incidentally). Aren't refoams usually just the surround (plus that piece of foam, if you're lucky)?

If that refers to the spider, one wonders whether just doing a re-cone would be better. If your spiders are in good shape, no sagging, why replace them?

Ralph856
08-08-2012, 10:15 AM
If that refers to the spider, one wonders whether just doing a re-cone would be better. If your spiders are in good shape, no sagging, why replace them?

Hmm, I guess he must have meant the spiders, then.

Yeah, those NIB drivers should have non-sagging spiders, if nothing else, having been supported in their boxes- so no need to replace them or do a recone from that perspective.

:cheers:

rdgrimes
08-08-2012, 11:25 AM
Fresh surrounds tend to make saggy spiders go away, so the best time to evaluate that is when there is an old or no surround at all. Any driver that's been sitting in one position for years can have sagging spider, which is why some people rotate drivers in the cab every few years or rotate them on the shelf.

Ralph856
08-08-2012, 03:04 PM
Any driver that's been sitting in one position for years can have sagging spider, which is why some people rotate drivers in the cab every few years or rotate them on the shelf.


I see.

Would you say, then, that there's no real point in paying more for a NIB driver (at least one that you cannot inspect beforehand)? Better off buying a cheaper used example and putting that cash into a recone, if necessary.

Feel free to be blunt :p






Fresh surrounds tend to make saggy spiders go away, so the best time to evaluate that is when there is an old or no surround at all.


I have that new pair (from my earlier thread) sitting here with disintegrated surrounds. I'd love to inspect the spiders before taking the next step, if I knew where the spiders actually were :crying:.

rdgrimes
08-08-2012, 08:30 PM
Bottom of the cone, the accordian-looking business.

I wouldn't say that you should assume any driver will need a re-cone, be it used or NOS/NIB. Either one might or might not. In any case a re-cone won't have white aquaplas, so there's that. For most folks its a matter of degrees and how well it works - or doesn't. I'd say that unless there's obvious issues, it's worth a re-foam.

Ralph856
08-09-2012, 11:43 AM
Bottom of the cone, the accordian-looking business.

I wouldn't say that you should assume any driver will need a re-cone, be it used or NOS/NIB. Either one might or might not. In any case a re-cone won't have white aquaplas, so there's that. For most folks its a matter of degrees and how well it works - or doesn't. I'd say that unless there's obvious issues, it's worth a re-foam.

Agree it looks more like an accordion than spider!

Doing a quick search and I cannot see any threads on the forum about how to visually inspect the spider for wear. Are there any pointers anywhere?

rdgrimes
08-09-2012, 08:27 PM
You're looking for sagging or leaning to one side. Obviously it depends on the foam suspension or lack of it. Normally it should be very flat.

Ralph856
08-10-2012, 06:03 AM
You're looking for sagging or leaning to one side. Obviously it depends on the foam suspension or lack of it. Normally it should be very flat.


Okay, thanks. One spider does seem to lean 'very slightly' downwards nearer the cone- or it could just be completely flat. In comparison, the other one seems to sit upwards more. It's not by much but there is a small difference between both spiders. This is with both their mildewed, disintegrated surrounds removed, so not influencing.

Looks like the first one could indeed have a small degree of 'sag'. Hopefully it's not enough to worry about..




My other repaired drivers have just arrived back. I didn't notice this before but the black plastic strip that is in between the surround and metal seems to have a bit of a gap in some places around it's circumference, but not in others. Is this a cause for concern?

56564

rdgrimes
08-10-2012, 09:32 AM
My other repaired drivers have just arrived back. I didn't notice this before but the black plastic strip that is in between the surround and metal seems to have a bit of a gap in some places around it's circumference, but not in others. Is this a cause for concern?

Shouldn't make any difference, but it's not particularly meticulous work. That plastic band (gasket) has a split so it can be moved and stretched or shrunk to fit. Somebody wasn't paying close attention when they glued it in.

DogBox
08-11-2012, 05:01 AM
Just a Question: The "foam piece" that covers the pole-piece vent-hole - evident when you first take out the old dust cap- Are they really necessary for the function of the speaker? Besides keeping foreign objects and grit from finding it's way into the coil gap?
I'm in that transition point myself and was thinking of a) replacing it with something else as acoustically transparent, b) leaving it out altogether and relying on the foilplate gauze on the back to be adequate. Interesting thread...

DogBox

4313B
08-11-2012, 05:32 AM
Prior to the foam discs JBL used phenolic mesh over the vent. The phenolic mesh wasn't sufficiently dense to do the job. I suppose grille cloth would work just fine. It's easy to cut a nice little cloth disc. Impregnate it with resin and make your own phenolic material that will last longer than you will.

DogBox
08-11-2012, 07:39 PM
wasn't sufficiently dense to do the job....
Hi 4313B, So, it "did" have a job to do...? What was it put in there for?
I would have thought it would give resistance to the flow of air behind the dust cap..???
Thanks,

DogBox

rdgrimes
08-11-2012, 08:21 PM
Keeps bugs out, for one thing.

DogBox
08-11-2012, 11:18 PM
Nothing else.... :confused:

Ralph856
08-16-2012, 03:41 AM
Okay, thanks. One spider does seem to lean 'very slightly' downwards nearer the cone- or it could just be completely flat. In comparison, the other one seems to sit upwards more. It's not by much but there is a small difference between both spiders. This is with both their mildewed, disintegrated surrounds removed, so not influencing.

Looks like the first one could indeed have a small degree of 'sag'. Hopefully it's not enough to worry about..
]

Hi rdgrimes

No comment on that? Is that degree of sag (if indeed it is sag) significant? What would be a sensible next step? (refoam, recone, throw in trash)

Thanks.....




Nothing else.... :confused:

Rats, lizards, and occasionally birds (depending on location)

Joking aside, I don't know how significant it is or whether the shop that removed it, replaced it with anything.

DogBox
08-28-2012, 02:20 AM
No comment on that? Is that degree of sag (if indeed it is sag) significant? What would be a sensible next step? (refoam, recone, throw in trash) , ....I don't know how significant it is or whether the shop that removed it, replaced it with anything.

Hi Ralph856,
If the spiders 'seem' ok, (there possibly will be a "slight" difference in the amount of "sag" between the two) and with the cost of just a 'refoam'..
..you may just find you have saved them! The spider AFAIK just keeps the voicecoil in alignment, without giving too much actual "support"- the job of the surround. From where I sit, JBL's were made for listening to... NOT for throwing in the trash...;).

Steve

grumpy
08-28-2012, 09:09 AM
The spider AFAIK just keeps the voicecoil in alignment, without giving too much actual "support"- the job of the surround

I don't think that statement can be made as being generally true.

For some drivers this may be true (suspension duties shared differently between spider and surround),
...but for drivers such as the LE10H, with a fairly thin foam surround, little on-axis support/stiffness/suspension
is available other than from the spider, whose performance remains critical,... the foam surround adding some resistive
damping and additional centering return force (keeping the cone and voicecoil from twisting off-axis).